Way back, before Everything, heck, before the Internet for me (coincidence or correlation?) when I was engaging in "sex", my girlfriend had, in her possession, a single red lightbulb.

Infra-red burns be damned, whatever room that mighty piece of glasswork was installed in underwent a magical and seamy transformation to a seedy den of wet smells and conspicuous bulges.

I was skeptical myself, but she converted me soon enough.

First person to make the "missionary" joke gets a whack in the kisser.